Spatio-temporal analysis of b-value prior to 28 April 2021 Assam Earthquake and implications thereof (original) (raw)
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Dipok K Bora
Government Model college, Deithor, Karbi Anglong-782 480, Assam, India
Rajib Biswas
Department of Physics Tezpur University Tezpur-784028 Assam India
Abstract
Here, we report a Spatio-temporal analysis of the frequency magnitude distribution of earthquakes (b-value) before the 28th April 2021 (Mw 6.4) earthquake event observed in northeast India. To esti- mate the average b-value for the study region, a data set of 750 earthquake events with magnitude Mw ≥ 3.9 is extracted from the homogenous part of the earthquake catalog (1950-2021) documented by the United States Geological Survey (USGS) and International seismological center (ISC) in the region. For spatial analysis of the disparities in b-value, the whole study region is subdivided into 16 square grids of dimension 1o×1o and the b-value is calculated for each subsection. In congruence with other studies, this work yields b-values ranging from 0.66 to 1.25. After the calculation of the b-value for each grid, it is observed that the grid with the epicentral location of the 28th April 2021 (6.4) earthquake has a low b-value. Accordingly, the spatial correlation and aberrant pattern between b-value and focal depth have been comprehensively explored. It is observed that the b-value sig- nificantly dips within a depth range of ~15-35 km which implicates high-stress accumulation and crustal homogeneity. The depth-wise variation in b-value infers the antithetical relationship between b-value and crustal stress. Mostly interplate earthquakes are observed in the study region; thereby hinting at intense seismicity at the upper crust.
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Sarma, V.; Bora, D. K.; Biswas, R. Spatio-Temporal Analysis of B-Value Prior to 28 April 2021 Assam Earthquake and Implications Thereof. Ann. Geophys. 2022, 65 (5), SE534. https://doi.org/10.4401/ag-8802.